1. Field of the Invention
The present invention relates to a coating and processing apparatus for applying a coating solution and removing the coating solution undesirably attached on the back and side surfaces of a mask substrate to be subjected to a light exposure step of a photolithographic process for a semiconductor device, and a method of coating and removing the coating solution.
2. Description of the Related Art
In manufacturing a semiconductor device and a liquid crystal display (LCD) device, a predetermined pattern is photolithographically formed on a photoresist film on a substrate by use of a mask substrate (reticle), that is, a so-called photolithographic process is performed. The predetermined pattern of the mask substrate is formed by forming a resist coating film on one of the surfaces of the mask substrate by spin coating and exposing the resist coating film to light to develop it.
Japanese Patent Application KOKAI No. 2000-271524 describes a coating apparatus for forming a resist coating film by applying a resist solution on a quadrangular substrate by spin coating. The coating apparatus has a spin chuck having a rectangular recess in the upper surface. When the quadrangular substrate is placed in the rectangular recess, the upper surface of the substrate is flush with that of the spin-chuck. While the quadrangular substrate placed in the recess is rotated by a spin-chuck, a resist solution is supplied to the upper surface of the substrate. After the supply of the resist solution is stopped, the substrate is still continued to rotate to cause airflow from the center of the substrate to the periphery along the surface of the substrate. Using the airflow, a solvent is vaporized from the resist solution. This is called “spin-dry”. As a result, a desired resist coating film is formed.
When the dimensional accuracy of a mask pattern is low, the accuracy of wiring width is significantly affected in all semiconductor wafers exposed to light with the pattern as a mask. Therefore, it is necessary to prevent particle attachment to the mask substrate as much as possible. The probability of attaching particles to the mask substrate is the greatest when the substrate is transferred immediately after a coating process. When a transfer arm member transfers a mask substrate, it is desirable to prevent the transfer arm member from being in contact with the mask substrate as much as possible. Actually, as shown in FIG. 8A, the regions 11 with which the transfer arm member can be in contact are limited only to four corners and the middles of four sides of the substrate G. Since the transfer arm member is prohibited from being in touch with a back surface 13b and a side surface 13e of the mask substrate, the support piece 52 of the transfer arm member is allowed in contact only with a chamfered C plane 13c, as shown in FIG. 8C.
However, when a resist solution is applied to a mask substrate by use of a conventional apparatus, the resist solution enters the recess, attaches to the side surface and back surface of the mask substrate and the attached resist solution is transferred to a transfer arm member, causing cross contamination. The cross contamination frequently occurs particularly at the corner portions of the substrate.
When the resist solution is supplied to a spin-rotating substrate G, it is radially dispersed along the surface (upper surface) 13a of the substrate G and shaken off from the substrate G by centrifugal force. However, as shown in FIG. 1, when a resist solution 100 reaches the periphery of the substrate G from the center of the substrate 13a, part of the resist solution changes its direction for the corners of the substrate, entering a clearance between the side surface 13e and the inner peripheral surface of the recess of the spin chuck. Further, the resist solution may possibly reach the back surface 13b of the substrate G. The corners of the substrate G are supported by support pieces 52 of the transfer arm member, the resist solution 100 is transferred from the substrate G to the support pieces 52, and further transferred from the support pieces 52 to another substrate G, causing cross contamination. Besides this, the resist solution thus transferred is dried into particles, which may deposit on another substrate G.